1. Field of the Invention
The invention relates to a vehicle position detection system that obtains a current position of a vehicle during travel, using a scenic image captured from a vehicle.
2. Description of the Related Art
In technical field of car navigation, a method in which information obtained from sensors such as a gyro sensor and a geomagnetic sensor is used (an autonomous navigation method), a method in which signals from GPS satellites are used, or the combination of the autonomous navigation method and the method in which signals from GPS satellites are used has been employed as a method of calculating the current position of a vehicle. Further, for example, a position measurement apparatus described in Japanese Patent Application Publication No. 2007-108043 (JP-A-2007-108043) is known as a position measurement apparatus configured to accurately calculate the current position (refer to the paragraphs 0009 to 0013, and FIG. 1). In the position measurement apparatus, first, a tentative current position is obtained using the signals from navigation satellites, and the like. Then, the coordinates of a feature point (a vehicle coordinate system feature point) of a road marking in a coordinate system (a vehicle coordinate system) with respect to the tentative current position are calculated using the captured image of a scene ahead of the vehicle. Then, the current position of the vehicle is calculated using the calculated vehicle coordinate system feature point and the stored coordinates of the feature point of the road marking (i.e., the coordinates shown in the world coordinate system). In the position measurement apparatus, it is possible to accurately calculate the current position, even when the position measured using the signals transmitted from the navigation satellites and/or signals transmitted from various sensors includes an error.
Also, in the technical field of car navigation, for example, in a navigation apparatus described in Japanese Patent Application Publication No. 2004-333233 (JP-A-2004-333233) (refer to paragraphs 0010 to 0043, and FIG. 1), a captured image of a building, a scene, or the like is used as a search key to retrieve at least one image with a high similarity degree from an image database, and the at least one retrieved image and corresponding location determination information are displayed to a user. When the user sees the at least one displayed image and the corresponding location determination information, the user selects the image from among the displayed image(s), and a destination is set to position information associated with the selected image. With this navigation apparatus, when a captured image obtained by capturing an image at a location is input, and search is performed, at least one image that matches the input image and the corresponding location determination information are retrieved and displayed to the user. When the user selects the image from among the displayed image(s), the destination is set to the location of the selected image. Thus, even when the user does not know the position of a location or the name of a facility to which the user wants to set the destination, the user can set the destination using the captured image obtained at the location.